Hi Lawrence and Jos   
      
   Thank you both very much for the information.  I am clearly wrong in my   
   understanding of electron spin preparation and I bow to your expertise.   
   I am very surprised though that I am wrong.   
      
   The main reason this issue arose is that I am comparing a geometric   
   algebra model wrt Bell's Theorem against what I know from QM. In QM when   
   measuring along a single axis I always assumed that a measurement only   
   indicated that the  axis pointed somewhere in the correct hemisphere,   
   rather than pointing exactly  parallel to the detector vector. (I   
   suppose this means that I never quite trusted quantisation enough.)  I   
   did follow 40 hours of Susskind's online "theoretical minimum" courses   
   on Entanglement and on QM, some years ago, which are quite mathematical.   
    I also know that a vector in 3D is not sufficient to completely define   
   a spin which requires QM and complex numbers etc.  But in geometric   
   algebra the idea of a spin bivector pointing in normal 3D (or what only   
   at face value appears to be 3D space as it has three orthogonal basis   
   vectors.) implies an exact spin direction in 3D.  So when the geometric   
   algebra model had every one of Alice's particles having its spin axis   
   exactly aligned parallel or antiparallel with Alice's detector vector, I   
   smelt a rat ... but I was wrong.   
      
   I also had thought that ...  given an electron precessing in a varying   
   magnetic field, then at some stage the particle axis could align exactly   
   parallel to the detector vector.  And maybe be detected at that point.   
   But as the electron is precessing, its axis's average direction would   
   not have been changed.  Ie it would continue to precess about the   
   original axis after detection.  But presumably that is wrong also.  I   
   had assumed that one could precess an axis about its original vector,   
   but that it was extremely difficult, if not impossible, to change the   
   original vector.   
      
   Finally, for Jos, as the problem concerned a  model disagreeing with   
   entanglement, I could not simply assume entanglement to be correct, even   
   if it is correct.   
      
   Thanks again.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)